Highly-accurate 5-axis flank CNC machining with conical tools

A new method for $5$-axis flank computer numerically controlled (CNC) machining using a predefined set of tappered ball-end-mill tools (aka conical) cutters is proposed. The space of lines that admit tangential motion of an associated truncated cone along a general, doubly curved, free-form surface is explored. These lines serve as discrete positions of conical axes in 3D space. Spline surface fitting is used to generate a ruled surface that represents a single continuous sweep of a rigid conical milling tool. An optimization based approach is then applied to globally minimize the error between the design surface and the conical envelope. Our computer simulation are validated with physical experiments on two benchmark industrial datasets, reducing significantly the execution times while preserving or even reducing the milling error when compared to the state-of-the-art industrial software

Virtual vibration absorber for active forced vibration reduction

<h2>Abstract</h2><p>Forced vibrations caused by unbalance can negatively impact the surface finish of high-precision grinding. This paper presents a model-free virtual vibration absorber control law, which effectively reduces vibration levels by emulating a physical vibration absorber. The control law's tuning parameters can be adjusted in real-time to track the spindle frequency, ensuring the excitation frequency always matches the anti-resonance created by the virtual vibration absorber. The control law is first experimentally validated on a flexure and then applied to a high-precision vertical grinding machine achieving a reduction of the forced vibration amplitude due to spindle unbalance by up to 85%.</p&gt

New feed rate optimization formulation in a parametric domain for 5-axis milling robots

When producing a numerical control (NC) program for a 5-axis CNC machine (the so-called milling robot) to mill a sculptural surface, a constant feed rate value is usually assigned based on programmer’s experiences. For this reason, the feed rate in most of NC programs is often not optimized, it is much lower than maximum reachable value. To increase the productivity of the machining process, the feed rate in NC programs for the milling robots need to be maximized. This paper proposes a new feed rate optimization model, of which the objective function and all the kinematic constraints are transformed and expressed explicitly in a parametric domain which is commonly used in the tool path generation process performed by current CAM systems. Thus, the optimal feed rate values along a parametric tool path can be computed in an effective and simplified manner. Numerical examples demonstrate the effectiveness of the proposed method

Chatter suppression techniques in metal cutting

The self-excited vibration, called chatter, is one of the main limitations in metal removal processes. Chatter may spoil the surface of the part and can also cause large reduction in the life of the different components of the machine tool including the cutting tool itself. During the last 60 years, several techniques have been proposed to suppress chatter. This keynote paper presents a critical review of the different chatter suppression techniques. Process solutions with design and control approaches are compiled to provide a complete view of the available methods to stabilize the cutting process. The evolution of each technique is described remarking the most important milestones in research and the corresponding industrial application. The selection of the most appropriate technique for each specific chatter problem is also discussed considering various aspects of machining processes